Algorithm 2 (ris, rif): = Find Stereo ROI (cams, camf, plmin).

cams, camf  SLAM camera, free camera (pose, intrinsic matrix)

plmin     minimum parallax considered meaningful

ris, rif    stereo ROI for images from cams and camf respectively

begin

distance: = FindDistance (cams.pose, camf.pose)

PyramidDepth: = FindMaxDepth (distance, plmin)

Py1: = ModelFoV(cams,PyramidDepth)

Py2: = ModelFoV(camf,PyramidDepth)

intersection = Ø

for each polygon_i in Py1

for each polygon_j in Py2

segment: = Intersect(polygon_i, polygon_j)

intersection.add(segment)

end for

end for

ris: = Ø; rif: = Ø

if (intersection = Ø) then

ris: = Envelope(ProjectTo2D(cams.pose, intersection.points))

rif: = Envelope(ProjectTo2D(camf.pose, intersection.points))

end if

end